Heat treatment of carbonaceous materials



Patented Mar. 11, 1941 PATENT OFFICE HEAT TREATMENT or CARBONACEOUSMATERIALS A Andrew McCulloch, Wiimslow, England No Drawing. ApplicationJanuary 14,1939, 'Serial No. 251,034. In Great Britain January 18,

2 Claims. '(01. 202-34) like carbonaceous material when mixed with or inthe presence of sulphur. or materials containing sulphur which is ableto react in the manner of free sulphur. The sulphur com- 15 bines withthe most reactive part of the material and is removed chiefly ashydrogen sulphide and as sulphur compounds in the tar.

The invention further comprises heating the carbonaceous materials withor in the presence 20 of sulphur or materials containing sulphur asabove specified towtemperatures of the order 150 C. to 450 ,6. followedby if desired a high heat treatment to temperatures of the order of 600to 800 C. p, v The invention further comprises the production of a cokewhich is active for the preparation of carbon disulphide by heating abriquetted ground mass of carbonaceous material and sulphur to atemperature of the order of 650 C. to 750 C., the sulphur content of themass being of the order of from 1 to thereof.

In one convenient application of the invention. a meta lignitous coal isground to pass through a '72 British standard sieve, and is mixed with2.75 parts of sulphur to .100 parts of the coal. the mixture beingbrlquetted. When carbonised at 120 C., the resulting coke produced thesame volume of carbon disulphide as was obtained from charcoal under thesame test conditions. The test consisted in the passage of a knownamount of sulphur vapour over the granulated coke or charcoal maintainedat 950 C., the volume of carbon disulphide produced being measured afterdistillation. It is noteworthy that coke produced from the coal itselfunder the conditions indicated, except that sulphur was not addedthereto, gave on test only one half the volume 01' carbon disulphide 0b50 tained with the use 01 sulphur in the briquetted mass.

The addition of proportions of sulphur larger .thanthe 2.75 parts aboveindicated gave only slightly increased yields 01' carbon disulphide. 55Ii however it is desired to produce veryreactlve alone.

coke: the maximum amount of tar and gas, and the minimum yield ofaqueous liquor, the proportion of sulphur in the mixture maybe increasedabove that which gives the best yield of carbon disulphide. Thus thecoal above indi- 5 cated ground as before and briquetted with five partsof sulphur per 100 partsoi coal gave on carbonisation at 600 C. aslightly increased yield of coke, a much increased yield of tar and acidfree gas and a greatly diminished yield of aquecos liquor. Theproportion of sulphur used is critical. When this is exceeded, the yieldof coke increases rapidly and'the yields of tar and gas diminish.

If only one part of sulphur per 100 parts of coal be used, the reactiveproperty of the result ant coke is considerably diminished but stillexceeds that of the coke produced from the coal As the proportion ofsulphur is increased to 2.75 per 100 parts of coal. the reactivity ofthe resultant coke rapidly increases. 9

The rank of coal to be used isnot critical except that coals must beemployed which under the treatment described give cokes of adequatestrength for the required purpose. Thus lignites may be employed, whilsthighly reactive cokes have been produced from bituminous-coals of goodcoking propensities. If the process is to be used for making coke forthe manufacture of 0 carbon disulphide or for the production of carbonfor solvent recovery purposes and the like, I prefor to use' coals ofthe meta lig'nitous class or the para bituminous class. I The size ofthe coal for admixture with the sulphur prior to briquetting depends on"the quality of the solid residue required and the nature 'of the otherproducts of carbonisatlon. 'llhe vhighest quality cokes are producedfrom the most finely divided coal but for such purposes as 40 themanufacture of carbon disulphide a meta lignitous coal ground to passthrough a '72 British standard sieve has been found suitable. If .theobject of the process is to improve the reactivity of coke for domesticpurposes, coal 5 of larger size is employed, the criterion being theadequate distribution of the sulphur in the material prior toitscarbonisation. Ii there is proper distribution, the coal may be usedwithout briquetting.

The quantity of sulphur to be used in a particular instance depends uponthe nature of the coal and its size, the conditions or heating, thebriquetting of the mixture 01' the use of unbriquettcd mixtures andthe.properties required 5 in the resulting coke and the yields and thenature of. the other carbonisation products. The,

most highly reactive cokes are obtained when larger quantities ofsulphur are used. If maximum yields of gas and tar are desired as wellas highly reactive coke, the quantity of sulphur used must be carefullyproportioned to the rank of the coal or to the type of materialemployed. The increased reactivity of the coke is shown by comparing theresults obtained with cokes prepared in the same manner from coal aloneand cokes prepared inthe same manner from the same coal of the same sizemixed with different proportions of sulphur.

The rate of heating and the final temperature to be attained depend onthe nature of the mixtures employed and the products of the treatmentwhich are desired. The procedure may be varied within wide limits. Ifthe aim is to produce a solid product which is smokeless on combustionor to reduce the smoke-producing propensities of a material the mixtureshould be heated for longer periods at less temperatures. Heating may becontinued for periods of the order of one hour and upwards, attemperatures of the order of 150 C. to 450 C. Thereafter the solidproduct may be heated to higher temperatures to remove furtherquantities of sulphur in combined condition. It high yields of solidresidue, low yields of tar and moderate yields of gas are desired themixture is heated at a slow rate, but if the aim of the application ofthe process is to secure the maximum yields of gas and tar, heating iscarried out more rapidly.

The process may be'applied to customary systems of carbonisation toproduce coke of greater reactivity than that normally produced. More orless uniform distribution of the sulphur in the charge of coal isrequired. The most reactive cokes are produced when appropriate mixturesof coal of suitable size and sulphurare carbonised at temperatures whichdo not exceed 800 C.

Cokes may be produced from coal-sulphur mixtures which are very hard.The hardness of the coke is in general determined by the factors alreadyenumerated. Carbonisation at 600 C. of mixtures of coal and sulphur indiffering proportionshas shown that with small proportions of sulphur,the sulphur content of the coke obtained is less than that of the cokefrom the original coal carbonised under like conditions.

With a properly adjusted proportion of sulphur in the mixture even at600 C., cokes may be produced as reactive as charcoal but containingless sulphur than coke made from the original coal alone carbonisedunder the same conditions.

Thus the above coal ground to pass a 72 British standard sieve mixedwith three parts of sulphur per one hundred parts by weight of coalbriquetted and carbonised at 600 C. gave a coke which contained 1.81 percent of sulphur. The coke from the untreated coal carbonised under thesame conditions contained 1.94 per cent of sulphur. The coke from amixture containing five parts of sulphur per one hundred parts by weightof coal carbonised under the same conditions contained 1.97 per cent ofsulphur. This latter mixture gave the maximum yield of tar and gas andthe minimum yield of aqueous liquor. With still larger proportions ofsulphur, the sulphur content of the cokes prepared at 600 C. increasedproportionately. If such cokes are however heated to higher temperaturesthe sulphur content diminishes. Thus using a mixture. containing tenparts of sulphur'per one hundred parts by weight of coal carbonisationat 800 C. gave a coke which contained only two per cent of sulphur.

Heating of the material to remove the sulphur which is in a combinedform, may be carried out in twostages; in the first stage temperaturesup to approximately 500 C. to 600 C. may be used. This removes the bulkof the combined sulphur. In the second stage a temperature up to 800 C.may be used when the smaller quantity of combined sulphur is evolved.This procedure lends itself to the ready and expeditious removal of thehydrogen sulphide from the combustible gases and for the recovery of thesulphur from the hydrogen sulphide by known methods. The sulphurrecovered by these methods may be re-used in the process.

If desired accelerating agents may be added to the sulphur-coal mixture.

Cokes produced by my process for the manu-' facture of carbon disulphidehave the advantage over cokes produced from coal alone in that they havea lower content of combined hydrogen.

The cokes produced by the use of my invention may possess or by suitabletreatment may have imparted to them highly absorbent properties 0 theproperties of decolouring carbons.

What I claim is:

1. In the preparation of a coke which is active for the preparation ofcarbon disulphide or suitable for the production of active carbon byknown methods, heating a briquetted ground mass of carbonaceous materialand sulphur or sulphur containing material in which the sulphur is ableto react in the manner of free sulphur to a temperature of the order of650 C. to 750 C., the sulphur content of the mass being of the order offrom 1 to 5% thereof. I

2. In the production of a coke which is active for the preparation ofcarbon disulphide or suitable for the production of active carbon byknown methods, heating a briquetted meta lignitous coal ground to passthrough a 72 British standard sieve mixed with 2.75 parts of sulphur to100 parts of the coal to a temperature of 720 C. at which carbonisationis completed.

ANDREW MCCULLOCH.

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